In industrial environments, compressed air is a very common means of actuating equipment. Compressed air may be used to operate a very wide variety of machines including presses, grinders, drills, torque tools, cleaning equipment, and painting equipment, among numerous others. Compressed air piping (also known as air lines) is a necessary utility in almost any industrial facility, similar to electrical wiring or water plumbing. The piping network typically consists of a series of rigid and/or flexible pipes of gradually decreasing diameters radiating from a central compressor or bank of compressors to all the various locations of tools within the plant, just as water pipes radiate from a main pipe through smaller supply lines to all tap locations. As with any other utility, compressed air comes at an expense to the operator. The air pressure in the lines, which actuates all of the machines connected to the network, is typically produced by one or more air compressors, which are generally powered by electric motors. Thus, increased usage of compressed air in a facility directly translates to higher electrical consumption. Minimizing compressed air usage benefits the plant operator by reducing electricity costs, and benefits the environment by reducing fuel consumption to generate electricity.
In addition to striving to minimize overall air consumption, it is also important that a compressed air system be properly configured such that it can adequately supply all of the equipment dependent on it. A system that is not balanced and operating at good condition may lead to additional expenses or downtime for the operator. For instance, if a compressed air line is inadequately sized, or if a leak exists, or if a compressor is unable to supply enough air, or if an air filter is clogged, there may be an inadequate air supply at a tool. This could for instance lead to a torque tool not applying enough torque to a fastener, leading to defective products and plant downtime required to identify and rectify the problem.
Because of the concerns listed above, it is common for industrial facilities to be subjected to periodic compressed air “audits,” which evaluate the usage of different parts of the compressed air system and identify potential issues which may lead to reduced productivity or increased cost and consumption. Example issues that could be identified might be air leaks, inadequate flow in a line, inadequate pressure in a line, excessive humidity in a line, clogged air filters, or an imbalance between different lines branching off from the compressor bank. Compressed air audits offer a valuable method to diagnose issues within a plant and improve its efficiency. However, there are several drawbacks to compressed air audits. First, by their nature, they are expensive events, requiring expensive airflow and pressure sensors and trained technicians to measure many aspects of the compressed air system and prepare a report. Because the equipment used is expensive, must be wired to receiver/analyzer equipment, and requires expert training to operate, it is impractical to buy many sensors and distribute them throughout the compressed air network. Instead, auditors use a few wired sensors and move them from one monitoring point to another over time to complete the audit. Further, it is impractical for most plant operators to perform in-house audits. Instead, outside firms are periodically hired to perform these audits, meaning data is collected infrequently, for instance every 6 or 12 months. This means that a problem condition could exist for many months creating additional costs and productivity problems before an audit would catch it.
A much more proactive and effective approach is to install a monitoring system consisting of a network of more inexpensive sensors throughout the compressed air system to monitor its health virtually continuously and identify problems as soon as they become detectable. An important component of such a system is an inexpensive but highly accurate sensor for measuring the air pressure inside the line, as well as the mass flow of compressed air through the line. An ideal embodiment of such a sensor would include a wireless radio for relaying the data from the sensor to a central receiving location, since plants can be quite expansive and running wires to a large number of sensors is impractical and costly. Deploying many such sensors throughout a compressed air network and sampling airflow and pressure data from them on a frequent basis, for instance every minute or every few seconds, would allow a plant operator to quantify the usage of different parts of the compressed air system, diagnose issues in real time, and implement solutions more quickly than traditional compressed air audits allow.
Novel solutions to these issues are presented in the following disclosure. It should be noted that while the background information provided and the sensor disclosed are targeted toward industrial compressed air, such a flow and pressure sensor could easily be adapted to measure the flow of additional fluids or gases other than air, including liquids.